1. Technical Field
This invention relates to an accelerator and alignment tube for use in a hydraulic food cutting apparatus and more particularly to a self sealing and quick change accelerator assembly.
2. Background Art
Many food products, particularly vegetables and fruits are processed prior to sale either by canning or freezing. Unless the product involved is of a naturally occurring edible size, for example peas, the product is usually trimmed and sliced, or diced, to edible size prior to preservation processing such as canning or freezing.
The slicing, dicing and other cutting operations have traditionally been accomplished with mechanical cutters. However, relatively recent advances in food product cutting technologies have resulted in the common use of hydraulic cutting apparatus which can be used to cut food products at relatively high speeds. Cutting capacities of 20,000 pounds to 35,000 pounds per hour are not unusual.
Hydraulic food cutters are used to cut a wide variety of food products, including potatoes, beets, zucchini and cucumbers, amongst others. The prior art relevant to the present invention are the food cutting devices themselves, and not the food product being cut. However, to place the present invention in proper context, and for purposes of clear illustration, this specification presents the prior art and the preferred embodiment in the context of a food cutter cutting potatoes. Cutting potatoes has been the most common application of the present machine. However, it should be distinctly understood that these hydraulic food cutters are capable of cutting and are used to cut a wide variety of food products.
In a typical prior art hydraulic cutting apparatus, where potatoes are to be cut, the potatoes are dropped into a tank filled with water and then pumped through conduit into an alignment chute or tube wherein the potatoes are aligned and accelerated to high speed before impinging upon a fixed array of cutter blades where the potato is cut into a plurality of smaller pieces.
The basic configuration of a prior art system is shown, in schematic format, in Prior Art FIG. 1. One of the components of a prior art hydraulic cutting apparatus for use in cutting potatoes is a receiving tank into which peeled or unpeeled potatoes are dropped. A food pump, usually a single impeller centrifugal pump, is provided. It draws its suction from the receiving tank and pumps water and the suspended potatoes from the tank into an accelerating tube which functions as the converging portion of a venturi. The accelerator tube is used to accelerate and align the potatoes immediately prior to impinging upon the stationary knife blades of the cutter blade assembly.
The use of an accelerator tube is required in order to perform two functions, first to accelerate the food product to the velocity required in order for it to pass cleanly through the knife blade assembly, and secondly to align and center the food products prior to their impinging upon the knife blade assembly.
In the case of potatoes the required velocity ranges from 40 feet per second to around 60 feet per second.
Each whole potato impinging upon the knife blade assembly passes through the cutting blade array and is thereby cut into a plurality of food pieces, for example french fry pieces, which pass with the water into the second half of the venturi which is a diverging tube in which the water and the cut food pieces are decelerated back to a slower velocity. The water and cut food pieces are then deposited onto a dewatering conveyer chain. The water passes through the dewatering conveyor chain and is collected and recycled back to the receiving tank. The cut food pieces remain on the conveyor chain and are carried off for further processing.
In the past, significant effort has been directed toward the development of good alignment or acceleration tubes which can properly align and accelerate the whole food product so that each whole food product is properly centered relative to the cutter blade array prior to impinging upon it. An examples of these efforts can be seen in my patent, U.S. Pat. No. 4,614,141 which teaches an alignment tube assembly which is used to accelerate and align whole potatoes immediately prior to impinging upon a cutter head array.
In the prior art the alignment tube is usually a two part assembly consisting of converging conically shaped metal or rigid housing, into which is inserted a more resilient liner, usually formed of reinforced food grade rubber. The larger inlet end of the tapered housing, in the prior art, is hard plumbed in some fashion or other to the discharge line or output of the centrifugal pump. Usually this is a bolted connection between a flange on the discharge line from the pump and a flange formed integral with input end of the housing.
At the other end, the resilient liner usually extends out a few inches from the convergent end of the outer housing. This extended end of the liner is inserted into the inlet hole of the cutter blade housing. In the better prior art designs the outlet of the accelerator tube liner ends immediately in front of the knife blade array. A water seal between the cutter blade housing and the accelerator tube assembly can be made by hard plumbing the accelerator tube housing to the cutter blade housing, but in more recent designs, this is not done because it is too difficult and time consuming to remove the housing for repair and maintenance.
Since the interface region between the accelerator tube assembly and the cutter blade housing is the narrowest part of the venturi, the hydraulic pressure at that point in the system is greatly reduced from that found at the discharge of the pump, usually in the range of two to ten pounds. As a result, instead of hard plumbing the outlet of the accelerator tube assembly to the inlet of the cutter blade housing, a series of packing rings are used. This is done to shorten the time required to disassemble and remove the accelerator tube assembly from the system. Here the problem is that each time the outlet end of the accelerator tube liner is removed from the inlet of the cutter blade housing, the packing rings should be replaced.
There are a number of reasons why accelerator tube assemblies must be periodically disassembled which include: cleaning; replacement of worn out liners; replacement of the liner with a different size liner; and to clean out a plug of uncut food product. The first three reasons are usually handled as scheduled maintenance items, and the time requirements, while significant are not critical. The fourth reason, the unscheduled and unwanted plug up of the system is a real problem since it often results in a complete shut down of a production line. Unfortunately, system plug ups are a fact of life in hydraulic cutting systems.
In the case of potatoes, production rates for hydraulic cutting systems usually run between 20,000 pounds to 35,000 pounds per hour. For potatoes, at 20,000 pounds per hour cutting rate, given an average 10 ounce potato, the number of potatoes passing through the cutter blade assembly is approximately 32,000 potatoes per hour, or approximately 8.8 potatoes per second. If one potato plugs the cutter blade assembly, in 10 seconds there will be 88 potatoes backed up behind the cutter housing in the accelerator tube assembly; in 20 seconds, 176 potatoes. At 35,000 pounds per hour the problem is further aggravated. In practice, if a prior art hydraulic cutting apparatus plugs while unattended, it is not uncommon for the plug to include backed up, smashed potatoes all the way back and into the food pump. A plug such as this can take hours to clean out since it requires substantial disassembly of the machine and its attendant piping. As a result, it is common practice in food processing plants to provide operating personnel to continuously monitor the operation of the hydro-cutting system.
What is needed is an accelerator tube assembly which can be quickly and easily disassembled and reassembled. That is the object of this invention.